This invention relates generally to charge coupled devices. More particularly, it relates to a monolithic ionic liquid-channel charge-coupled device (ILC-CCD) and methods of making the same.
The ability to quickly and to accurately analyze liquids to determine their constituents is of great general importance, and of particular importance in the biomedical research industries. Over the years, a variety of techniques have evolved that can analyze a solution and determine its component parts. These techniques can be divided into two basic categories. The first category includes fast and simple techniques, which detect only a few specific constituents. Devices which perform this technique include ion selectable electrodes, such as pH electrodes. A drawback of this general category is that, although the techniques are relatively fast and relatively simple to perform, they only detect specific sample constituents. Thus, a particular device is typically used to detect a relatively few, predetermined sample components.
The second category includes techniques which can be used to detect a broader range of constituents. Such techniques include ion mass spectrometers, gas chromatographs, and blood serum chemistry analyzers. A drawback of this general category is that the techniques require relatively large amounts of time and equipment to perform a complete analysis of the solution constituents. In addition, relatively large amounts of personnel, with their associated costs, are required to monitor and perform the analyses.
Some prior art techniques have sought to address the above problems by incorporating integrated circuit (IC) theory and technology into the device design and fabrication. IC technology has led to the development of smaller, more cost effective devices that are capable of detecting a broader range of constituents. Moreover, by incorporating IC technology, techniques can now be employed that incorporate previously inaccessible physical principles.
One such physical principle that would be beneficial in analyzing liquid samples is the physical principles employed by charge-coupled devices. Conventional charge coupled (CC) devices exist for generating a stream of electrons in response to an input signal, such as incident ambient light. Consequentially, CC devices are employed in many types of imaging devices, such as video recorders, camcorders, cameras and the like. Prior art CC devices usually consist of an array of polysilicon-silicon dioxide capacitors, typically mounted on a substrate. The substrate typically has a top face to which an insulating layer of silicon dioxide (SiO.sub.2) is applied. A series of gate electrodes are then mounted to the silicon dioxide layer at various locations above the substrate. Each gate electrode has an associated electrical connector that communicates with an alternating current (AC) voltage source. The interface between the silicon dioxide layer and the substrate top face forms an electron channel. The channel defines the region in the CC device where electrons accumulate.
During operation of the CC device, a voltage is applied to each gate at a selected occurrence rate, called a stepping frequency. Typically, the electrons accumulate in packets under the gate electrode with the highest potential, e.g., most positive. The electron packets can be moved to the right or to the left of that gate by biasing the voltages positively on either adjacent gate, and biasing the gate above the packet negatively, such that the electrons move along the channel from regions of low potential to regions of high potentials.
There still exists a need in the art for improved analytical devices that can detect the components of a liquid solution. One particular advantageous device would employ the physical principles associated with CC devices. Additionally, a device that can relatively easily and relatively quickly determine all the ionized constituents of a liquid sample would present a major improvement in the art. Moreover, a device that is relatively easy to manufacture, that is relatively low-cost, and that is capable of detecting the presence of minute concentrations of a sample component would also present a major improvement in the art.